The long-range research goals have remained basically the same for several years. We have continued to study a variety of heterogeneous and homogeneous charge transfer processes for the purpose of attaining an understanding of transfer mechanisms. These have over the past few years been directed to the study of stoichiometry (n values), energetics (E degree ' values) and kinetic parameters of bioelectron transfer components such as heme proteins through coupling via a mediator-titrant to electrodes. The indirect coulometric titration method has proved to be particularly valuable in these studies. Cytochrome c oxidase and other components present in intact submitochondrial particles have been studied using this method. More recently the redox properties of the cytochromes in vesicles of anerobically-grown paraccocus denitrificans have been evaluated. An important part of our efforts has been the continued development of theory and methodologies associated with charge transfer processes. For example, we have devoted major effort for several years to spectroelectrochemistry using optically transparent electrodes. More recently, our attention has been directed toward the design, fabrication, testing and analysis of chemically modified surfaces for the purpose of creating catalytic and/or selective electrodes.